In a Thin Film Transistor Liquid Crystal Display (TFT-LCD), there generally exists a capacitance between the gate electrode and the source electrode of the TFT switch. When the TFT is turned off, the gate voltage is switched from a high level to a low level. Due to existence of the gate-source capacitance, voltage at the pixel electrode is also pulled down by the capacitive coupling effect and therefore deviated from the voltage preset by the system. As illustrated in FIG. 1, when the gate voltage VG for driving the TFT is a positive voltage, the pixel voltage Vp is smaller than the preset voltage value. In contrast, when the gate voltage VG for driving the TFT is a negative voltage, the pixel voltage Vp is greater than the preset voltage value. Specifically, the pixel voltage Vp is deviated from the preset voltage value by the following deviation amount:ΔVp=(VGH−VGL)*CGS/(CLC+CST+CGS)  Equation 1
The equivalent circuit of FIG. 1 is illustrated in FIG. 2. It is known from Equation 1 that the influence on the pixel voltage by the variation of gate voltage is mainly determined by the voltage difference between the turn-on and turn-off voltages of the gate electrode (VGH, VGL), the gate-source capacitance (CGS), the liquid crystal capacitance (CLC) and the storage capacitance (CST).
To overcome display defects caused by the pixel voltage deviation, conventional LCDs generally compensate the pixel voltage deviation by using the voltage of the common electrode (Vcom). As illustrated in FIG. 1, it may set Vcom as equal to −ΔVp, thereby eliminating the influence caused by the pixel voltage deviation. However, the method is deficient in that the gate-source capacitance CGS of the LCDs is not a constant, which will make the deviation amount of the pixel voltage Vp relative to the preset voltage value varied. As a result, it is difficult to compensate the pixel voltage deviation by using a single common voltage, which will in turn affect rotation direction of the liquid crystal, thereby generating different transmittivity for liquid crystal molecules under the positive drive voltage and the negative drive voltage. In this way, due to the liquid crystal molecules in affected rotation direction, human eyes can perceive an obvious screen flicker. Screen flicker lasting for a long time will make the human eyes uncomfortable and adversely affecting the user experience.